The plasma membrane and its component molecules make selectve permeability possible .
What you intend the students to learn about this idea.
In all biological organisms, each cell is enclosed by a selectively permeable membrane which regulates what gets into and out of the cell.
The plasma membrane comprises of two layers of phospholipid molecules as well as protein, carbohydrate and cholesterol molecules (fluid-mosaic molecule).
The process of diffusion moves substances down a concentration gradient, from regions of high concentration to regions of low concentration.
Diffusion of water across a selectively permeable membrane is called osmosis; osmosis results in net movement of water from a solution with a high concentration of water (low concentration of solutes) to a solution with a low concentration of water (high concentration of solutes).Students will need to learn the terms hypertonic, hypotonic and isotonic.
Active transport requires the expenditure of energy in which the net movement of a dissolved substance occurs against its concentration gradient.
Why it is important for students to know this.
The cell membrane is perhaps the most significant part of the cell. It is important for students to understand the composition of the cell membrane in order for them to understand how the membrane carries out different roles (ie. Cell-cell recognition, restricting movement of substances between one part of the cell and another etc.)
Diffusion, osmosis and active transport are key concepts to understanding many important biological processes. Diffusion is the primary method of short distance transport in a cell. Osmosis is the key to understanding water intake by plants, water balance in land and aquatic organism, turgor pressure in plants, as well as transport in living organisms.
What else you know about this idea (that you do not intend students to know yet).
At Unit 1 (Area study 1), students are not required to know about:
·Fick’s Law of diffusion ·Details of the sodium- potassium pump ·Membrane potential ·The electrogenic and proton pump- ion pumps that generate voltage across membranes ·Osmoregulation ·The structure and function of intergral and peripheral proteins in the cell membrane.
Knowledge about students’ thinking /difficulties connected with teaching this idea.
Students may confuse the cell membrane with the cell wall. Some students may use the terminology interchangeably.
Students may find it difficult understanding concentration gradient. It may be challenging trying to explain to students the increase and decrease in density of a chemical substance.
Students may memorise or recognise the definitions of these concepts (diffusion, osmosis and active transport) without really understanding their meanings. Students may engage in a lot of rote learning and therefore not be able to answer questions that require application of knowledge or abstract thinking.
Teaching procedures (and particular reasons for using these to engage with this idea).
Specific ways of ascertaining students’ understanding or confusion around this idea (include likely range of responses).
Think-Pair-Share Have students work with a partner and brainstorm everything they know about the cell membrane. As a class compile all the ideas students have come up with and list these on the board.
Concept maps Using the ideas students have brainstormed instruct them to create a concept map summarising everything they know about this concept. Reassure them that it is ok if they can’t make many links at this stage. The concept maps can be used to assess prior knowledge and gives the teacher a reference point to build on students understanding. The concept map can also be used to help identify any alternative conceptions students hold about these concepts.
Unit 1- Area of Study 1
BIOLOGY IDEA:
The plasma membrane and its component molecules make selectve permeability possible
.
The plasma membrane comprises of two layers of phospholipid molecules as well as protein, carbohydrate and cholesterol molecules (fluid-mosaic molecule).
The process of diffusion moves substances down a concentration gradient, from regions of high concentration to regions of low concentration.
Diffusion of water across a selectively permeable membrane is called osmosis; osmosis results in net movement of water from a solution with a high concentration of water (low concentration of solutes) to a solution with a low concentration of water (high concentration of solutes). Students will need to learn the terms hypertonic, hypotonic and isotonic.
Active transport requires the expenditure of energy in which the net movement of a dissolved substance occurs against its concentration gradient.
Diffusion, osmosis and active transport are key concepts to understanding many important biological processes. Diffusion is the primary method of short distance transport in a cell. Osmosis is the key to understanding water intake by plants, water balance in land and aquatic organism, turgor pressure in plants, as well as transport in living organisms.
· Fick’s Law of diffusion
· Details of the sodium- potassium pump
· Membrane potential
· The electrogenic and proton pump- ion pumps that generate voltage across membranes
· Osmoregulation
· The structure and function of intergral and peripheral proteins in the cell membrane.
/difficulties connected with teaching this idea.
Students may find it difficult understanding concentration gradient. It may be challenging trying to explain to students the increase and decrease in density of a chemical substance.
Students may memorise or recognise the definitions of these concepts (diffusion, osmosis and active transport) without really understanding their meanings. Students may engage in a lot of rote learning and therefore not be able to answer questions that require application of knowledge or abstract thinking.
(and particular reasons for using these to engage with this idea).
There are various online videos that can be used to demonstrate these biological processes. Often they are much better quality and more recent than the video collections available at most schools. Students benefit by having information presented to them in different forms. Utilising these resources helps to create a rich learning environment.
Cell membrane
http://www.youtube.com/watch?v=Qqsf_UJcfBc&feature=related
Diffusion
http://www.youtube.com/watch?v=gXJMBgyT_hk
Osmosis
http://www.youtube.com/watch?v=sdiJtDRJQEc
Biological animations with corresponding Multiple Choice Test
Animations can be used to either introduce a concept or to complement the teacher’s explanations. These animations can be set up on an interactive whiteboard and the class can work through the questions as a group. Some schools have access to a class set of laptops; in this case students can work through the animations and answer the questions individually.
Diffusion
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html
Osmosis
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html
Active Transport
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html
Experiments that utilise the P.O.E procedure
There are numerous experiments students can conduct to investigate diffusion and osmosis. Some of these are listed below. Similarly students could be given specific materials and be asked to design their own experiment that demonstrates the concepts of diffusion or osmosis. In both situations students would be required to complete a Predict-Observe-Explain (P.O.E) table.
//http://faculty.clintoncc.suny.edu/faculty/Michael.Gregory/files/Bio%20100/Bio%20100%20Laboratory/Diffusion%20and%20Osmosis/Diffusion%20and%20Osmosis.htm//
//http://www.spartechsoftware.com/reeko/Experiments/ExpSpinelesPotatoes.htm//
Plasma membrane activities
These activities are designed to cater to individual learning styles.
· Students can use craft items and butches paper to put together a physical representation of the plasma membrane. Students will be given a list of all the structures to include in their diagram.
· Students can choose to either create a song or perform a role play outlining the structures and functions of the cell membrane.
(include likely range of responses).
Have students work with a partner and brainstorm everything they know about the cell membrane. As a class compile all the ideas students have come up with and list these on the board.
Concept maps
Using the ideas students have brainstormed instruct them to create a concept map summarising everything they know about this concept. Reassure them that it is ok if they can’t make many links at this stage. The concept maps can be used to assess prior knowledge and gives the teacher a reference point to build on students understanding. The concept map can also be used to help identify any alternative conceptions students hold about these concepts.